This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Seasonal affective disorder (SAD), regularly occurring fall/winter depression that improves in spring/summer, affects over 14.5 million Americans. For acute (current) and long-term (future) SAD management, available clinical practice guidelines recommend daily use of light therapy from onset of first symptom through spontaneous springtime remission during every fall/winter season, generally spanning 3 to 6 months of the year. Light box therapy is the best available SAD treatment and effectively treats acute SAD. However, long-term compliance with the treatment is poor because it is burdensome and time-consuming. Alternative SAD treatments are needed to prevent the return of depression each fall/winter season. An ideal alternative treatment to light therapy would be time-limited (i.e., acute treatment completed in a discrete period vs. daily treatment every fall/winter indefinitely), effectively treat acute SAD, and show effects that endure beyond the end of treatment to prevent the annual return of these disabling symptoms. Cognitive-behavioral talk therapy (CBT) is a time-limited treatment that is effective for acute nonseasonal depression and appears to have benefits that extend beyond the end of treatment to reduce risk of relapse (the return of depression symptoms after an initial improvement with treatment) and recurrence (the onset of a brand new depressive episode). The Principal Investigator (PI) has developed a new cognitive-behavioral talk therapy for SAD and tested it in two prior small-scale studies. These prior studies suggest that CBT may be as effective as light therapy for acute SAD treatment and that CBT may be superior to light therapy during the next winter season 1-year later. This NIMH R01 project is a larger, more definitive study that has potential to impact clinical practice. The randomized clinical trial will compare standard light box treatment to our CBT treatment over a 6-week trial in the initial winter and at followup visits conducted in the next two winters. This study proposes to enroll 160 qualified participants during the fall/winter season of the first 4 project years. We anticipate that we may need to consent and screen up to 3X this number of potential participants to reach our enrollment goal. Participants will be recruited from media advertisements and from flyers posted in the community and in local clinics. The 160 enrolled participants will be randomly assigned to one of two 6-week treatments: 80 to light box therapy (30-min/day in front of a standard light box with administration time and duration individually-adjusted after the first week) and 80 to cognitive-behavioral talk therapy (1 'bd-hr twice-weekly group therapy). Mood will be monitored weekly during the 6-weeks of study treatment with a semi-structured interview, and participants will complete some questionnaire measures at pre-treatment, mid-treatment (after 3-weeks), and at post-treatment. Participants will return for followup during January or February of the next two winter seasons (i.e., 1- and 2-years after treatment completion). A third in-person followup will occur in the August following study treatment completion to assess summer mood status. Two brief tracking telephone calls will be made to participants in the time between summer followup and the first winter followup to track any recurrences and any new treatments initiated with the first call in October and the second in December.